Microbial production of methionine is reviewed with 73 references. The review describes different methionine-producing organisms, as well as analog-resistant regulatory mutants, their optimum cultural conditions and yields. The pathways of methionine biosynthesis and their regulation are discussed.

By mutagenesis with N-methyl N-nitro-K-nitrosoguanidine, in two steps, a number of methionine plus threonine double auxotrophs have been isolated from a glutamate producing Arthrobacter globiformis, excreting L-lysine in good amounts. For the three potent mutants tested the medium of WHITE was adjudged to be the best. Biotin, ammonium chloride and glucose was found to be optimum at 5 pg 1-1, 40 mM and 4% level, respectively. With such optimal C and N source, the strain M'I 35 yielded 28.0 g lysine I-' of medium in flask culture.

A number of lysine plus threonine double auxotrophs have been isolated from a ethionine resistant methionine producing strain of Brevibacterium heali previously isolated from soil by mutagenesis with N-methyl N-nitro-N-nitrosoguanidine in two steps. This strain excreted L-methionine in sufficient amounts. For the three potent mutants tested, the medium of ALFOLDI was judged to be the best. Biotin and ammonium nitrate were found to be optimal at 5 pg/I and at a 40 mM level, respectively. With such an optimal dose, the strain BhLT 27 yielded 25.5 g/1 methionine in a flask culture containing methionine-analogue ethionine at a minimal inhibitory concentration.

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